1. Field of the Invention
The present invention relates to a magnetic recording medium. More particularly, it relates to a magnetic recording medium which has an improved still characteristic.
2. Description of the Prior Arts
One of the important characteristics required for a magnetic recording medium is a still characteristic. In order to impart excellent still characteristic in a recording and reproducing operation of a video tape recorder, it is necessary to prevent the wearing of the surface of the tape by a head of the video tape recorder. In one system, during the still reproducing operation, two magnetic heads are placed with a gap of 180 degree to a rotary drum and are rotated at high speed with a tape in a circular loop form to perform a scanning. In this system, if the wearing resistance of the tape is not satisfactory, the surface of the tape is gradually scooped out to shorten the still reproducing time. Therefore, it is necessary to prevent a wearing of the tape under the magnetic head scanning at high speed whereby the still reproducing time is prolonged.
Heretofore, in order to improve the still characteristic, it has been proposed to incorporate a hard non-magnetic powder which is harder than a magnetic powder in a coated layer of the magnetic tape. The typical conventional hard non-magnetic powders are as follows:
Oxides: Al.sub.2 O.sub.3, SiO.sub.2, Cr.sub.2 O.sub.3, CeO.sub.2, BeO, ZrO, TiO.sub.2 ; PA1 Carbides: B.sub.4 C, SiC PA1 Nitrides: TiN, Si.sub.2 N, BN, AlN; PA1 Metal: Zr
The wearing resistance of the magnetic tape having the magnetic layer containing such hard non-magnetic powder has been improved. Recently, a narrow track head has been used for imparting high recording density, serious requirement for shortening a reproducing time has been noted. As a reference, the relations of the reproducing outputs and the reproducing times for a head having a width of 100.mu. and a head having a width of 60.mu. are shown in FIG. 1. The reproducing time for the head having a width of 60.mu. is remarkably shortened. It has been required to used fine magnetic powder having smaller particles. This is disadvantageous for the still characteristic. In order to overcome such disadvantages, it has been required to improve the still characteristic by further improvement of the wearing resistance of the type as the magnetic recording medium.